Pumping process employing a liquid sorbent



June 21, 1966 E. BLAUTH 3,256,576

PUMPING PROCE SS EMPLOYING A LIQUID SORBENT Filed Nov. 2, 1961 5 Sheets-Sheet 1 June 21, 1966 E. BLAUTH PUMPING PROCESS EMPLOYING A LIQUID SORBENT 5 Sheets-Sheet 2 Filed Nov. 2, 1961 Evid .BLQLLU? I flttornes June 21, 1966 E. BLAUTH PUMPING PROCESS EMPLOYING A LIQUID SORBENT 5 Sheets-Sheet 3 Filed NOV 2, 1961 I Flttovne Edd .BL cunt 35:

June 21, 1966 BLAUTH 3,256,676

PUMPING PROCESS EMPLOYING A LIQUID SORBENT Filed Nov. 2, 1961 5 Sheets-Sheet 4.

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Qttovnag ii-A I l-I Ti-l a 0 5 United States Patent 3,256,676 PUMPING PROCESS EMPLOYING A LIQUID soRuENT Erich Blauth, Munich, Germany, assignor to Max-Planck- Gesellschaft zur Forderung der Wissenschaften E.V., vertreten durch 1 Max-Planck-Institut fur Physik und Astrophysik, Munich, Germany Filed Nov. 2, 1961, Ser. No. 149,643 Claims priority, application Germany, Nov. 8, 1960, M 47 060 7 Claims. (c1. 55-43 The present invention relates generally to pumping processes, and more particularly to such processes for generating high and maximum vacuums especially those oflering a high rate of evacuation at extremely low pressures.

Despite theincreasing importance and use of ultrahigh vacuums in physics and industry, there is still an cannot be heated to a sufliciently high temperature and therefore do not solve the problem. Since these pumps are not capable of being heated to a high enough temperature there is an intense evolution of gas which limits the finally attainable vacuum-to comparatively low values.

Diifusion pumps, which may also be used for creating vacuums, are limited as to the final vacuum which may be obtained due to back diffusion (see Fliigge, Handbuch der Physik, XII, page 582). This is also brought out in the McGraw-Hill Encyclopedia of Science and Technology, volume 14, page 242, wherein it is stated Diffusion pumps sulfer from back-streaming of the operating fluids However, although this eflectmay be diminished by arranging several diflusion pumps in tandem, the expense is very great. The pump fluid of a dilfusion pump absorbs gas during the preliminary stage of creating a vacuum, and this fluid transports the gas into the evaporator or boiler from which it again reaches the nozzle and has to be pumped away again. In the past, in order to avoid deterioration or loss of the vacuum thereby elfected, the pump fluid condensed during the preliminary stages of creating the vacuum has been subjected to a cleaning operation in a rectifying column before being reintroduced into the evaporator (Opitz, Schneider, Vakuumtechnik 9, 104, 1960).

Other processes for creating high vacuums are known wherein the gas molecules to be removed to create the vacuum are placed onto a movable carrier in a high vacuum chamber, and are transported by the carrier into a chamber having a lower vacuum, where they are removed from the carrier. This carrier may be in the form of a band or disc, onto which the gas molecules are placed. Placing the molecules thereon may be promoted by ionization of the residual gas and by an electric guide field such as is disclosed in German Patent No. 1,046,249. Due to the limited surface area of the carrier, known pumps operating according to this process have comparatively low rates of evacuation of the vessel or chamber in which the vacuum is to be created.

A Getter pump is also known in which liquid metal, having a fairly low vapor pressure, for example gallium, which is highly degassed, is forced to rain in fine drops in a sorption chamber. In a second chamber, separated from the sorption chamber by a seal of liquid metal, the

3,256,676 Patented June 21, 1966 liquid metal which has rained down in fine drops is degassed under high vacuum and at high temperature, and after cooling it is reintroduced into the first chamber by means of a pump and a nozzle. A disadvantage of this pump is that the drops raining down in the sorption chamber have only a relatively small surface area. Also, it is extremely diflicult to provide a cycle of circulation of molten metal by means of a circulation pump, if extreme metal purity requirements are made. When such a plant or pump is placed into operation, all the components used in the circulation of molten metal must initially be heated above the melting temperature of the metal. The servicing and maintenance of this known type of pump is therefore comparatively cumbersome. Moreover, the pump is relatively expensive, creates noise, and requires constant care and attention.

With these defects of the prior art in mind, it is a main object of the present invention to provide a pumping method for providing extremely high vacuums with rapid rates of evacuation, in a manner which is efficient in operation and relatively modest in cost.

Another object of this invention is to provide process of the type described wherein the pump fluid or sorbing medium may be degassed and purified for continuous use during any operation.

A further object of this invention is to provide a method in which the pump fluid or sorbing medium provides a relatively large surface area for the sorption of gases, in comparison to its volume.

These objects and others ancillary thereto are accomplished according to preferred embodiments of the invention, wherein the gas molecules to be withdrawn in order to create the vacuum, are sorbed in a high vacuum chamber by a pump fluid or sorbing medium. The gas molecules are transported by the fluid into a chamber having a lower vacuum where they are desorbed. The sorbent is introduced into a sorption chamber in the form of a preferably wet vapor and at least a portion thereof is deposited and/or condensed along the walls of this chamber.- In this manner new sorbent is continuously condensed on the surface of the droplets of sorbent descending in the sorption chamber, and fresh sorptive surfaces are continuously provided. The gases which have already been sorbed are enclosed within the droplets and an extremely high rate of evacuation is possible even when working with extremely high vacuums.

To facilitate sorption, the sprayed liquid and/or vaporized sorbent may be ionized by means which are known per se. At the same time the residual gas may be ionized by giving it a charge opposite that of the ionized sorbent vapor, or in some other manner which is known per se. In order to cause ionization the following or any other suitable means may be used: a high frequency gas discharge, a Penning discharge, an electron ray which, if necessary, will be used in connection with a magnetic field, and a radioactive radiation source.

Mercury is preferably the liquid sorbing medium. However, there are other inorganic or organic liquids which may be used, although they should have a low vapor pressure and good stability. For example, pump fluids may be used which have extremely low vapor pressures, such as those suggested by Hiclcmann, a well known authority in the field.

The sorbed gas may be liberated from the liquid sorbent and this may be accomplished by heating and/or evaporation of the pump fluid in a separate regenerating chamber. Regeneration of the pump fluid may also be accomplished by an electric glow discharge, are discharge, or other known physical or chemical processes for cleaning or degassing liquids of sorbed gas. This regeneration might also be done by a simultaneous or successive combination of such processes. Any cleaning or decontamination of gases from the liquid sorbent may not change or decompose the sorbent if such a change will impair operation of the sorption pump. Therefore, glow and arc discharges generally will not be applicable with organic sorbents, which substances may be thoroughly decontaminated by heating and atomization using a high voltage.

It has to be emphasized that a sorption pump according to the invention differs basically from a known diffusion pump. The well known operation of a diffusion pump is in short about as follows: A gas molecule entering the jet stream of the pump experiences collisions with the vapor molecules of the jet. The jet itself is pointed away from the side to be evacuated and thus the gas molecules are transported by momentum transfer to the low pressure side.

The nozzle, the pumping area, the vapor delivery rate and other design and operation parameters of a diffusion pump have to be carefully chosen to provide satisfactory pumping speeds and pressure differences.

It is well known that the vapor jet of a diffusion pump has to be dry so that only vapor molecules are present and not droplets or the like. Thus adsorption of gas by the vapor cannot occur because adsorption can only occur if accumulations comprising a greater number of molecules are present.

As opposed to a known diffusion pump the gas molecules are adsorbed to liquid droplets and withdrawn with the collected liquid in the sorption pump according to the invention rather than being pushed into the lower vacuum region by collisions with vapor molecules as in a diffusion pump. The outstanding speed and pump capacity of the present sorption pump results from the fact that not only droplets of the sorbing agent are present, the surface of which may be relatively soon covered by adsorbed gas molecules and thus saturated, but also condensable vapor which continuously creates new surfaces onto the droplets so that further gas will be adsorbed and the formerly adsorbed gas molecules are buried under the newly condensed surface layers. Thus in the present pump the vapor introduced into the sorption chamber it wet, i.e., the temperature corre sponds substantially to the boiling point of the sorbent under the existing pressureconditions. The whole volume filled with the droplets-vapor mixture is involved in the pumping action in the present case rather than only a comparably small area where the high vacuum section and the vapor jet communicate in a diffusion pump. v

The back diffusion which mainly limits the ultimate vacuum of a diffusion pump is negligible in the present sorption pump. Thus vacua of mm. Hg and lower have been attained.

The process comprising the present invention may also be used in connection with rotating high vacuum pumps, and particularly molecular or turbomolecular pumps. In such pumps the rotor and stator are coated with a liquid film by condensing or spraying the sorbent thereon. This film will sorb the residual gas contained in the device, as well as the gas given off by the pump during operation thereof. A particular advantage is obtained when using this process with rotating molecular pumps because the interior of the pump is rapidly heated by the heat of condensation of the sorbent being used to create the liquid film, and thus the operating temperature is quickly reached, and the evolution of the gas caused by the heating, is terminated.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a diagrammatic sectional view of a sorption pump for carrying out the process according to the present invention.

FIGURE 2 is a diagrammatic sectional view of another embodiment of the invention.

FIGURE 3 is a diagrammatic sectional view of a combination sorption pump and diffusion pump.

FIGURE 4a is a diagrammatic sectional view of a combination sorption pump and a rotating molecular pump, while FIGURE 4b is a diagrammatic elevational end view of this combination.

FIGURE 5 is a diagrammatic sectional view through a further embodiment of the invention.

FIGURE 6 is a diagrammatic plan view of the pump illustrated in FIGURE 5.

FIGURE 7 is a diagrammatic sectional view of still another embodiment of a sorption pump.

FIGURE 8 is a diagrammatic sectional view of a regenerating device which is especially suitable for the decontamination or cleaning of mercury.

FIGURE 9 is a diagrammatic sectional view of a regenerating device similar to FIGURE 8 but wherein both electrodes are disposed in the nozzle.

FIGURE 10 is a diagrammatic sectional view of still another embodiment of a regenerating device.

FIGURE 11 is a diagrammatic sectional view of a regenerating device which is especially suitable for the regeneration of organic liquids.

With more particular reference to the drawings, FIG- URE 1 illustrates a pump having a housing 1 defining a sorption chamber 1 which is in communication with a vessel (not shown) to be evacuated via a pump intake 2 of suitable cross-sectional area. Bafiles or cooling traps may be provided between sorption chamber 1 and the vessel or container, and this is especially expedient if mercury is used as the sorbent. A liquid capable of sorbing the residual gas in the vessel is injected into the upper portion of sorption chamber 1 through nozzle 3. Mercury and practically all of the oils normally used as pump fluids for diffusion pumps are suitable for this purpose. The reason for this is that large surface areas are available, so that good rates of evacuation may be obtained even if the sorptive power of the liquid itself is relatively small.

A pump 4 forces liquid sorbent through conduit 3 to nozzle 3. As the liquid is discharged through this nozzle it is hurled and splashed against the somewhat bulging upper wall 101 of sorption chamber 1. In this manner a uniform liquid film is formed which descends along the side walls of this chamber. In addition, the interior of the chamber is filled with a mist of fine drops or droplets which slowly descend and in their travel also sorb residual gas molecules. Within the sorption chamber itself, further surfaces may be provided to increase the area which is covered with sorbent, as will be described in detail below.

When using very stable liquids, such as mercury, the sorption may be aided and abetted by ionizing the residual gas and/or the liquid carrier in chamber 1. This may be accomplished by means of an induction coil 5 which is fed from a high frequency source. If desired this may be accomplished by other means which are known per se as mentioned hereinabove.

The liquid, which is charged with the residual gas, collects in the lower portion of the sorption chamber and passes through a siphon 6 to a cleaning or regenerating device 7 in which the gas is freed from the liquid. In FIGURE 1 this device is illustrated as a rectifying column. The sorbing medium, which is charged with gas, flows over the inlet 8 of this rectifying column and moves downwardly while being heated by the rising vapor from the liquid collected at the bottom of reservoir 9. Thus, the sorbed gas is liberated and the sorbing medium is decontaminated of the gas. A conduit 10 is connected to the top of the rectifying column and is in communication with a pump (not shown), preferably a diffusion pump, which is connected on the outlet side thereof and by means of which the gases thus liberated are removed. A cooling jacket 11 surrounds conduit 10 and acts as a reflux condenser. The liquid which has been freed of the sorbed gas passes from reservoir 9 through a conduit 12 and cooler 12, and is then reintroduced into chamber 1 via nozzle 3 by means of pump 4.

Another embodiment is illustrated in FIGURE 2 where; in a highly purified liquid is vaporized in a boiler 13. The vapor ascends through chimney 14, flows out of nozz'e 15, and is directed against the upper wall of sorption chamber 1. This nozzle 15 may be cooled by cooling coils 16 so that the vapor issuing from the noZZle is a wet vapor mixed with droplets. A heat insulating covering 17 is provided about the portion of chimney 14 which is disposed within the sorption chamber 1. This covering is provided to prevent heating of the sorbing medium, which is present in the sorption chamber and which would otherwise be heated at the chimney and release the gas while in the sorption chamber, which is undesirable. A cooling jacket 18 surrounds sorption chamber 1 and is supplied with a cooling liquid which flows invia a short feed pipe 19, and which flows out via a suitable coolant outlet 20.

The liquid sorbent which has been charged with gas is coll cted in a trough 21 at the lower portion of sorption chamber 1. This trough is led through a conduit 122 passing through the cooling jacket 18. This conduit 122 is spaced from chimney 14 so that heating and consequent release of the gas from the liquid is prevented. The liquid in conduit 122 is conducted through a regenerating device 22, which is not shown in detail, and after-the liquid'is freed from the gases, it returns to boiler 13.

In the pump illustrated in FIGURE 2, the vapor of the sorption liquid issues toward the chamber wall above pump intake 2, and preferably against the upper end wall of the sorption chamber 1. The advantage of this arrangement is that the vapor density is comparatively small at the point where pump intake 2 communicates with sorption chamber 1. By means of this arrangement the gas to be removed may easily enter the sorption chamber 1 through intake 2.

Preferably, an arrangement is provided to control the amount of cooling performed by cooling coils 16 with respect to the nozzle. This cooling is independent of the cooling of sorption chamber 1. The temperature of the wet vapor issuing from nozzle 15 should be such that the sorbent is discharged as a mist of liquid and in gaseous form as well. C-ondensable vapor is present in the sorption chamber 1 and the result is that new liquid layers are condensed both on the wall and on the descending droplets so that new sorptive surfaces are continuously formed.

The sorbent should be capable of wetting the walls of the sorption chamber easily. Therefore, if mercury is used the wall is preferably provided with a coating which forms a comparatively stable amalgam together with mercury. Under some circumstances it is also advantageous to roughen or abrade the walls of the sorption chamber.

Another embodiment of a pump is illustrated in FIG- URE 3 wherein the sorption pump is combined with a diffusion pump. The diffusion pump may be designed in a manner known per se and is provided with a deflecting cap 23 which is preferably insulated. A pump which. is preferably also a diffusion pump, has its inlet connected to a short feed pipe 24. The jet chimney 25 of the diffusion pump, which in this embodiment is il lustrated as having one stage, may concentrically circle the chimney 14 of the sorption pump. If desired a portion of the ascending vapor in chimney 14 may be branched off for the diffusion pump. The sorption stage and the diffusion pump operate with the same pump fluid. Preferably, the liquid introduced into the diffusion pump has been previously subjected to a degassing operation before evaporation. Instead of the common boiler 26 and the common cooler 27, separate boilers and coolers may be used. The sorbent which is charged with the residual gas could flow through the diffusion pump to the cleaning device 22'. However, preferably it is collected in a trough 21 and the suction slot 28 of the diffusion pump is protected by means of a droplet screen 29 whereby disturbances of the diffusion pump by refluxing sorbent are avoided.

This droplet screen 29 is selectively movable from the solid 'line position 29 illustrated in FIGURE 3, to the dashed line position 29 and vice versa. Any means, many of which are known per se, may be used to move this droplet screen, for example a magnetic device.

When placing the pump illustrated in FIGURE 3 into operation, the container or vessel to be evacuated is first preferably evacuated as much as possible by means of the diffusion pump, and only then is the sorption stage placed into operation. If this is always done first, impairment of the evacuation rate of the diffusion stage caused by mist or vapor in the sorption chamber 1 is avoided. As the final vacuum which may be created by the diffusion pump is approached, the sorption stage is connected. This may be done, for example, by opening a cut-off valve (not shown) in the chimney 14, or by placing a separate boiler into operation. When the sorption stage has attained full operational capacity, droplet screen 29 may be lowered into the position indicated by 29', so that none of the gas in the diffusion pump can diffuse back into the sorption chamber 1. At the prevailing pressures, even if there are narrow fissures, a sufficient seal is formed, and the droplet screen may immerse into the liquid which is disposed in trough 21.

The gas laden sorbing medium is introduced to a'cleanin-g device 22 from the trough 21 via a conduit 30. In device 22 the condensed pump fluid of the diffusion pump introduced through a conduit 31, is decontaminated of the gas. Even when the droplet screen 29 is lowered into position 29', the diffusion pump is preferably allowed to continue operation since the circulation of pump fluid through the cleaning device further cleans the Mid which serves at the same time as the sorbing medium. The cleaning or regenerating device and the diffusion pump may be connected to the same pump which has its inlet connected thereto to remove the gas.

InFIGURE 4a, a longitudinal section of a simplified turbomolecular pump is illustrated, and FIGURE 4b illustrates an end elevational View thereof. The turbomolecular pump is one constructed according to Becker, an authority in the field, and contains a rotor 32 having discs 32' projecting therefrom, as well as a stator 33 also containing discs 35' which intermesh with the rotor discs. The gas is withdrawn from the container or vessel to be evacuated through a pump intake 34. A subsequent pump stage may be connected at port 30.

The operation of such a pump may be improved by introducing a vaporized or atomized sorbing medium into the pumps. In FIGURE 4a this is accomplished by nozzle 35, which introduces this medium into a pump. By doing this, the elements of the pump are uniformly covered with a thin liquid layer which sorbs both the gas to be removed as well as the gases liberated from the elements of the pump during operation. By using such an expedient, the fact that this pump is relatively difiicult to heat is not of great importance since the above-described action will aid in the heating.

When the sorbing medium is introduced into the pump, the elements thereof are rapidly heated by the heat of condensation in conjunction with the heat supplied externally, and therefore quickly assume the final operating temperature. More vapor may be initially introduced through nozzle 35 than will be introduced during the continuous operation of the pump, so that it will be heated above the normal operating temperature. This temperature may be maintained at any desired point by supplying external heat or by using heat insulation, together with the accumulation of heat effected by the pump. After the degassing operation which occurs due to this action, the vapor supplied to nozzle 35 may be throt'tled and the external heat supply may be switched off or the heat insulation removed so that a slightly lower operating temperature may be secured by selfadjustment of the arrangement.

The gas laden sorbent passes through narrow grooves 36 which are disposed in the walls of pump housing 132 and collects in a channel or trough 37 at the bottom of the pump. The sorbent is withdrawn and degassed before being recirculated to nozzle 35. The dimensions of the grooves 36 are such that there is a capillary effect and they will be capable of holding the sorbing medium. In this manner the effective distances between the periphery of the rotor discs and the opposing stator wall will remain constant even when there is a diminished quality of sorbent passing from nozzle 35.

Since a vaporous sorbent is available for operation of the nozzle 35, there is a possibility of connecting a diffusion or vapor jet stage between the molecular pump and the auxiliary pump. [With such an arrangement the back diffusion through the turbomolecular pump may be further reduced without substantially increasing the expense involved.

Another arrangement is illustrated in FIGURE wherein a sorption pump is combined with -a diffusion pump. The pump intake 2 is actually an extension of the sorption chamber [1. The sorbent is vaporized and passes through a chimney '14 and a nozzle 40, into the sorption chamber 1, in a similar manner as in the embodiments of FIG- URES 2 and 3. The nozzle 40 is preferably cooled by use of cooling coils '16.

It is to be noted that the shape of this nozzle and its distance from the wall are such that a diffusion pump effect cannot be created. The nozzle serves only to supply droplets and vapor of the sorbent which sorbs the residual gas and removes it from the chamber. In order to provide a larger area 'for sorption, a plurality of radially extending wings 4 1 are arranged interiorly of the sorption chamber I1. The liquid sorbent may be deposited on these wings, which extend into the vicinity of chimney 14 and may be recessed in the portions thereof in the vicinity of the nozzle.

FIGURE 6 is a plan view of the pump illustrated in FIGURE 5 looking down into the pump intake 2. The arrangement of the radially extending wings 41 may be seen with respect to the deflecting cap 42 and the droplet screen 29, as well as collecting trough 21. The other elements of the pump illustrated in EIGU RESS and 6 may be similar to those of the pump illustrated in FIGURE 3, and accordingly corresponding parts are designated by identical reference numerals.

In another embodiment of the pump illustrated in FIGURE 7, the chimney '14 extends downwardly from above through cooling j a-cket27 and into the interior of sorption chamber .1. Since chimney 14 is cooled, a wet vapor is released from the nozzle. Deflecting cap 42' is designated so that the mist vapor mixture is conducted generally laterally and upwardly. In a manner similar to that of -a fractionating column, the interior of the sorption chamber 1 is provided with a'plurality of inserts 0r trays 43 over which the sorbent flows and then falls downwardly. These inserts are preferably punched sheet metal plates arranged at specified distances from one another. With this arrangement the surface area avail- :able for sorption may be substantially increased.

A number of decontaminating or regenerating devices for removing gas from the gas laden sorbent is illustrated in the embodiments of FIGURES 8 to 11, which decontaminating devices may take the place of device 7 in FIG- URE 1, and devices 2 2 and 22 in FIGURES 2 and 3, respectively. The device shown in FIGURE 8 is particularly suitable for the decontamination of mercury. The gas laden sorbent passes into a chamber 1-50 through conduit 30 which has an outlet defined as a nozzle 50. A first electrode 51 is introduced into nozzle 50 from above,

.and a second eleclfpdfi 521s arranged in the nozzle from below. During operation an arc is generated between these electrodes. This arc atomizes and 'v-aporizes the liquid issuing from nozzle 50 and the gas that is given off is withdrawn by a pump connected at the outlet side through a pump intake 53. p

This pump intake 53 is surrounded by a cooling jacket '54 having a baflle 55 which is also cooled. In this manner, the sorbent will not flow into the pump connected at the outlet side. The degassing in chamber 56 may be aided by a high frequency discharge provided by coil 57. Also, plates 58, which are preferably heated, may be arranged in chamber 56 to enhance the action. Below regenerating chamber 56 is a condensing chamber 59 which is surrounded by a cooling jacket 60. The cleaned sorbent is returned to recirculate through the device by means of a conduit 61. Another device, similar to that in FIGURE 8, is illustrated in FIGURE 9. In this device the electrodes 51' and 52' are both disposed in the nozzle from the sides and oppose one another.

Another regeneration device is illustrated in FIGURE 10 wherein a glass or porcelain frit 70 is provided through which the gas laden sorbent may flow into regeneration chamber 56". This chamber, similar to the sorption chamber of the embodiment illustrated in FIGURE 7, is filled with plates 71, which may be in the form of punched ceramic discs or the like. A gas discharge is maintained in chamber 56" by means of a coil 7 2 which is heated by a high voltage. This discharge effects a desorption or liberation of the gas from the sorbing medium. This desorbed gas is removed by a preferably cooled pump intake 53.

Another regeneration device is illustrated in FIGURE 11, and this device is particularly suitable for the regeneration of organic fluids. A nozzle 50 is provided with a metallic rim 151 which can be connected to a high voltage source through a lead wire 51". With this arrangement, the gas laden sorbent issuing from nozzle 50 is sprayed electrostatically. An arrangement of substantially parallel inclined short pipes is disposed below nozzle 50' and the fine mist electrostatically sprayed from the nozzle falls into this arrangement. From this point the mist falls due to gravity into a broiler 81 which may be heated in any suitable manner. The rising vapor heats the pipes 80 and feeds chimney :14 which is connected with a nozzle for issuing the sorbing medium into the sorption chamber.

All of the described examples may be modified in many respects to suit particular purposes. However, fundamentally all of the processes for the fine distribution of liquids to aerosols or for vaporization may be used both in the sorption chamber 1 and in the desorption or decontamination chambers serving for regeneration of the sorption medium. But the parameters must be chosen so that the desired effect will be obtained. The liquid sorbent may also be sprayed, if desired, by means of a type of spray gun. In this event, vaporized sorbent serves as pump fluid and the liquid is introduced with as little difference in level as possible.

Besides using the single escape or discharge nozzle illustrated in the embodiments, several such nozzles may be used. If desired sorbent in vapor or mist form may be taken off or branched off from the chimney by suitable apertures and caused to flow int-o the sorption chamber. A sorption pump according to the present invention may be very effectively used in combination with other pumps and preferably pumps of the diffusion type. The rate of evacuation of diffusion pumps exhibits selective minimums for difiFerent gases, which minimums are lower than those corresponding to the molecular weight in each case. The reason for thisis a sorption of the gas which is already removed, which sorption occurs in the auxiliary vacuum chamber of the pump. The effect of this is that this gas returns to the nozzle together with the pump fluid and thus impairs the vacuum. By means of the 1. A process for creating a high vacuum comprising I the steps of: placing a high vacuum pumping zone in communication with a vessel to be evacuated; forming a liquid sorbent into the the form of a wet vapor containing droplets and introducing said wet vapor into said pumping zone in a direction to deposit at least a portion of said vapor and droplets upon the walls defining said zone for sorbing the molecules of a gas to be removed from said vessel; maintaining said pumping zone sufficiently cool for continuously condensing said sorbent upon its introduction into said zone; removing the resultant liquid from the high vacuum pumping zone to a lower vacuum desorbing zone; and desorbing the gas from said sorbent in said desorbing zone.

2. A process as defined in claim 1, wherein a pump intake places the pumping zone in communication with said vessel, said vapor being introduced into said pumping zone by being conducted against a portion of an inner wall thereof above said pump intake for causing the sorbent to rain down in said zone.

3. A process as defined in claim 1, wherein the liquid sorbent is one selected from the group consisting of mercury and an organic liquid having a very low vapo pressure.

4. A process as defined in claim 1, wherein the liquid sorbent is an organic liquid having a very low vapor pressure of the type used as pump fluid for difiusion pumps.

5. A process as defined in claim 1, comprising spraying and heating the liquid sorbent to accomplish the step of desorbing.

6. A process for creating a high vacuum, comprising the steps of:

placing a high vacuum pumping zone into communication with a vessel to be evacuated which is at a higher pressure than the pumping zone and contains a g forming a liquid sorbent into a wet vapor containing droplets;

introducing the wet vapor into said pumping zone in a direction to deposit a portion of said vapor and droplets upon the walls defining said zone; condensing the wet vapor from the time it is introduced into said zone to form droplets which contact the gas; sorbing the gas into the droplets;

removing the resultant liquid from the high vacuum pumping zone to a lower vacuum desorbing zone;

desorbing the gas from said sorbent in said desorbing zone; and

recycling the sorbent from the desorbing zone to where it is formed into a wet vapor.

7. A process for creating a high vacuum comprising the steps of:

placing a high vacuum pumping zone into communication with a vessel containing a gas to be evacuated and which is at a higher pressure than the pumping zone;

forming a liquid sorbent into a wet vapor containing droplets;

introducing the wet vapor into and distributing it throughout said pumping zone;

continuously condensing the Wet vapor from the time it is introduced into said zone .to form additional droplets which contact the gas and rain down in said zone and continuously forming on the descending droplets freshly condensed sorbent to form freshly condensed surfaces;

sorbing the gas into the freshly condensed surfaces on the droplets; and

removing the descended sorbent from a lower portion of the pumping zone.

References Cited by the Examiner UNITED STATES PATENTS 2,063,249 12/ 1936 Hansell 230-69 2,246,327 7/ 1941 Slepian 230-69 2,839,238 6/1958 Bock 230-101 2,841,323 7/1958 Lindenblad 230-69 2,931,561 4/ 1960 Hiesinger 230-101 2,934,258 4/ 1960 Power 230-101 2,984,314 5/ 1961 Denton -387 3,050,236 8/1962 Batzer 230-69 3,071,310 1/1963 Hayashi et al. 230-69 3,098,155 7/ 1963 Becker 230-69 3,134,534 5/1964 Jancke et al 230-101 FOREIGN PATENTS 1,071,891 12/1959 Germany. 1,104,652 4/ 1961 Germany.

552,904 4/1943 Great Britain.

REUBEN FRIEDMAN, Primary Examiner.

LAWRENCE V. EFNER, J. H. BRANSON, JR.,

. Examiners.

R. M. VARGO, B. NOZICK, Assistant Examiners. 

7. A PROCESS FOR CREATING A HIGH VACUUM COMPRISING THE STEPS OF: PLACING A HIGH VACUUM PUMPING ZONE INTO COMMUNICATION WITH A VESSEL CONTAINING A GAS TO BE EVACUATED AND WHICH IS AT A HIGHER PRESSURE THAN THE PUMPING ZONE; FORMING A LIQUID SORBENT INTO A WET VAPOR CONTAINING DROPLETS; INTRODUCING THE WET VAPOR INTO AND DISTRIBUTING IT THROUGHOUT SAID PUMPING ZONE; CONTINUOUSLY CONDENSING THE WET VAPOR FROM THE TIME IT IS INTRODUCED INTO SAID ZONE TO FORM ADDITIONAL DROPLETS WHICH CONTACT THE GAS AND RAIN DOWN IN SAID ZONE AND CONTINUOUSLY FORMING ON THE DESCENDING DROPLETS FRESHLY CONDENSED SORBENT OT FORM FRESHLY CONDENSED SURFACES; SORBING THE GAS INTO THE FRESHLY CONDENSED SURFACES ON THE DROPLETS; AND REMOVING THE DESCENDED SORBENT FROM A LOWER PORTION OF THE PUMPING ZONE. 